Everywhere: Rename {Deprecated => Byte}String

This commit un-deprecates DeprecatedString, and repurposes it as a byte
string.
As the null state has already been removed, there are no other
particularly hairy blockers in repurposing this type as a byte string
(what it _really_ is).

This commit is auto-generated:
  $ xs=$(ack -l \bDeprecatedString\b\|deprecated_string AK Userland \
    Meta Ports Ladybird Tests Kernel)
  $ perl -pie 's/\bDeprecatedString\b/ByteString/g;
    s/deprecated_string/byte_string/g' $xs
  $ clang-format --style=file -i \
    $(git diff --name-only | grep \.cpp\|\.h)
  $ gn format $(git ls-files '*.gn' '*.gni')

AK/JsonValue.cpp

@@ -155,7 +155,7 @@ JsonValue::JsonValue(long long unsigned value)
 }
 
 JsonValue::JsonValue(char const* cstring)
-    : JsonValue(DeprecatedString(cstring))
+    : JsonValue(ByteString(cstring))
 {
 }
 
@@ -167,7 +167,7 @@ JsonValue::JsonValue(double value)
 }
 #endif
 
-JsonValue::JsonValue(DeprecatedString const& value)
+JsonValue::JsonValue(ByteString const& value)
 {
     m_type = Type::String;
     m_value.as_string = const_cast<StringImpl*>(value.impl());
@@ -175,7 +175,7 @@ JsonValue::JsonValue(DeprecatedString const& value)
 }
 
 JsonValue::JsonValue(StringView value)
-    : JsonValue(value.to_deprecated_string())
+    : JsonValue(value.to_byte_string())
 {
 }